So to cut the story short I am interested in studying Networking and Security and I haven't applied for any courses yet. I wanted to prepare myself a little by studying for a year on my own while working then applying next year for a Bachelor course and if all goes well do my Masters.

Without knowing much about the subject, here is some generic advice peppered with questions that will hopefully lead you in the right direction:

First, I'm assuming you have a college/university or two in mind to apply to, and that you have some kind of entrance score that is decent enough to get into said courses (if not, those are probably the things you should be working on). Look up the information on the relevant courses - there should be some kind of course directory or something that will discuss things like the available courses, requirements for graduation, etc. Look at some of those, particularly the 1st year courses. Do they have any prerequisites or "recommended" previous knowledge? If they do, and you're not too strong in those areas, do some study in them. I did a couple of courses where I didn't have the recommended previous study, and they were extremely tough because the lecturer just assumed everyone was well-versed in them.

If you're all good in that stuff, then if there are course outlines, see what the first couple of topics covered are going to be, and look up some material based on those. You will cover the same stuff again when you take the course, but having a decent feel for the basic concepts means you will hit the ground running (and, hopefully, get you into the habit of doing reading *before* the relevant lecture, so the lecture serves as a way to consolidate your knowledge rather than just sitting there and letting it wash over you). If there's a recommended textbook for the course, see if you can access it, possibly by visiting the college library. However, *don't* buy it, because there's a decent chance a newer edition of the same book will be released and that will be the required version when you take it, and even if they change nothing else they tend to switch around the exercise questions to make it harder to use previous editions.

I am actually a mature age student, I was studying in another IT course but never ended up finishing due to complications. But I have around 90% of the units completed so its just a matter of enrolling again and doing a weeks worth of work...

Is there anything in particular that would make me have a higher chance of being accepted, is there anything I can say or do or does it all come down to meeting entrance requirements and being lucky?

I think you have decided right choice for completing a course in networking and security. Even it is tough to study it has number of scopes in the field of networking. So i think it is better for you to complete the networking courses like CCNA or CCNP. There are number of courses are available in the web and so you can search for the same in the Google.